Power utilities generate electrical power at remote plants and deliver electricity to residential, business or industrial customers via transmission networks and distribution grids. The power utilities may transmit large quantities of electric power over long distance transmission networks from power generating plants to regional substations, which then supply the power to local customers using the distribution grids.
The transmission networks and/or distribution grids may include overhead power transmission lines suspended by towers or poles. The transmission lines may, for example, be bare wire conductors made of aluminum. Instead of aluminum, copper wires may be used in medium-voltage distribution and low-voltage connections to customer premises.
Power loss in transmission lines (in particular, in long distance transmission lines) is a significant component of the cost of electricity. This power loss is a decreasing function of transmission voltage. Therefore, power is typically first transmitted as high voltage transmissions from the remote power plants to geographically diverse substations. The most common transmission voltages in use are 765, 500, 400, 220 kV, etc. Transmission voltages higher than 800 kV are also in use. From the substations, the received power is sent using cables or “feeders” to local transformers that further reduce the voltage. Voltages below 69 kV are termed sub transmission or distribution voltages. The outputs of the transformers are connected to a local low voltage power distribution grid that can be tapped directly by the customers.
The conductors in overhead power transmission lines are supported by or suspended from insulators (e.g., by pin-type and suspension-type insulators, respectively). For sub transmission or distribution voltages, both types of insulators are commonly used in overhead power transmission lines. However, for transmission voltages, only suspension-type insulators are commonly used in overhead power transmission lines.
The mechanical and electrical qualities of the insulators in use directly affect the integrity of a suspended or supported overhead transmission line. Insulators can fail, for example, because of surface contamination, aging, manufacturing defects and damage due to mishandling. Insulator failures are associated with a majority of line outages and most of line maintenance costs.
In practice, commercial electricity transmission networks and distribution grids (collectively “the network” or “the grid”) may have complex topologies interconnecting several power plants, regional substations, and load centers. The grid may include multiple redundant lines between network points or nodes so that power can be routed from any power plant to any load center, through a variety of routes, based, for example, on network conditions, power quality, transmission path economics and power cost. Grid operators may control operation of the grid by managing generators, switches, circuit breakers, relays, and loads. Industrial control system techniques may be used for this purpose. For example, the grid may be coupled to common centralized, distributed or networked control systems (e.g., Supervisory control and data acquisition systems (SCADA)), which electronically monitor and control the entire or most of grid. The electronic control actions may be performed automatically by remote terminal units (“RTUs”) or by programmable logic controllers (“PLCs”). Communication in the control systems between different control elements and grid components may use microwaves, power line communication, wireless, and/or optical fibers.
“Smart” grids may further use modern digital technologies (e.g., automation, sensing and measuring, and communication technologies) to upgrade distribution and long distance transmission grids. The digital technologies may allow grid operations to be improved for increased power quality, reliability, efficiency, uptime, and safety. The digital technologies may allow various distributed power generation and grid energy storage options to be included in the grid, and reduce grid failures (e.g., power grid cascading failures).
Consideration is now being given to improving electricity grids. In particular, consideration is now being given to solutions for keeping insulators, which are in use in overhead power transmission systems, healthy. Some such solutions may prevent insulator failure and reduce line outages and/or line maintenance costs. Further, consideration is being given to improvements directed to alternate or non-traditional grid components for flexible management of grid operations. Additionally, consideration is being given to testing the voltage carrying capability of overhead power transmission lines.